Chemistry - Chapter 4
the line emission spectrum of an atom is caused by the energies released when electrons
"jump from a higher energy level to a lower energy level
All forms of electromagnetic radiation move at a constant speed of
3.00 x 10^8 meters per second through a vacuum and at a slightly slower speeds through matter
what are the frequency and wavelength ranges of visible light?
400nm - 700nm
What is the speed of all forms of electromagnetic radiation in a vacuum?
All forms of electromagnetic radiation move at a constant speed of 3.00 × 10^8 meters per second (m/s) through a vacuum
Explain the mathematical relationship among the speed of electromagnetic radiation.
All forms of electromagnetic radiation move at a constant speed of 3.00 × 10^8 meters per second (m/s) through a vacuum and at slightly slower speeds through matter.
Substituting c/λ for v into the equation of energy gives the following:
E = hv, v = c/λ, E = hc/λ
one wave/second is called a
Hertz (Hz)
Describe the Bohr model of the hydrogen atom.
Niels Bohr proposed a hydrogen-atom model that linked the atom's electron to photon emission.The electron can circle the nucleus only in allowed paths, or orbits. The energy of the electron is higher when it is in orbits that are successively farther from the nucleus. When an electron falls to a lower energy level, a photon is emitted, and the process is called emission. Energy must be added to an atom in order to move an electron from a lower energy level to a higher energy level. This process is called absorption.
Max Planck proposed that the relationship between a quantum of energy and the frequency of radiation is
Quantum of Energy = hv
The photoelectric effect is
The emission of electrons from a metal when light shines on the metal
the significance of the photoelectric effect and the line-emission spectrum of hydrogen to the development of the atomic model
The photoelectric effect shows the emission of an electron from a metal when the light is shined on it. The 4 different lights that appeared when a light was shown through a prism is part of the line, which is the emission spectrum.
How are wavelength and frequency of electromagnetic radiation related?
Wavelength and frequency are mathematically related
How is hydrogen's emission spectrum produced?
While in a given orbit, the electron is neither gaining nor losing energy. It can, however, move to a higher-energy orbit by gaining an amount of energy equal to the difference in energy between the higher energy orbit and the initial lower-energy orbit. When a hydrogen atom is in an excited state, its electron is in one of the higher-energy orbits. When the electron falls to a lower energy level, a photon is emitted, and the process is called emission. The photon's energy is equal to the energy difference between the initial higher energy level and the final lower energy level. Energy must be added to an atom in order to move an electron from a lower energy level to a higher energy level. This process is called absorption. The energy of each absorbed or emitted photon corresponds to a par ticular frequency of emitted radiation, Ephoton = hν.
Particles that carry a quantum of energy is called
a proton
hydrogen's line-emission spectrum
a series of specific frequencies of emitted electromagnetic radiation
Higher energy light has
a shorter wavelength than lower-energy light
There are many possible excited states that each have
a unique energy
an electron in an atom can move from one main energy level to a higher main energy level only by
absorbing an amount of energy exactly equal to the difference between the two levels
Energy must be added to an atom in order to move an electron from a lower energy level to a higher energy level. This process is called
absorption
An electron can move to a higher-energy orbit by gaining an
amount of energy equal to the difference in energy between the higher energy orbit and the initial lower-energy orbit
The energy of the electron is higher when it is in orbits that
are successively farther from the nucleus
In the equation c = λν,
c is the speed of light (in m/s), λ is the wavelength of the electromagnetic wave (in m), and ν is the frequency of the electromagnetic wave (in s-1).
In the equation c=λv,
c is the speed of light, λ is the wavelength of the electromagnetic wave, and v is the frequency of the electromagnetic wave. Because c is the same for all electromagnetic radiation, the product λv is a constant
Because c is the same for all electromagnetic radiation, the product λν is a
constant
When the electron is in one of these orbits, the atom has a
definite, fixed energy
Wavelength (λ) is the
distance between corresponding point on adjacent waves
the unit for wavelength is a
distance unit
In the early twentieth century, light was determined to have a
dual wave-particle nature
In 1905, Einstein expanded Planck's theory by introducing the radical idea that
electromagnetic radiation has a dual wave-particle nature
According to the Bohr model of the atom, which particles are allowed to exist in any one of a number of energy levels?
electrons
Quantum theory states that
electrons can exist in atoms only at specific energy levels
The process of an atom releasing energy when it moves to a lower energy state is called
emission
When an electron falls to a lower energy level, a photon is emitted, and the process is called
emission
When an electron falls to a lower energy level, a photon is
emitted, and the process is called emission
The photonś energy equals the
energy difference between two sublevels
in order for an electron in an atom to change from the ground state to an excited state,
energy must be absorbed
Electromagnetic radiation is a form of
energy that exhibits wavelike behavior as it travels through space
frequency and wavelength are mathematically
equal to each other: c=λv
hydrogen atoms can be
excited by whatever amount of energy was added to it
a state in which an atom has a higher potential energy than it has in its ground state is an
excited state
the energy of a photon is directly related to its
frequency
While in a given orbit, the electron is neither
gaining nor losing energy
The lowest energy state of an atom is its
ground state
the lowest energy state of an atom is its
ground state
Planck's Constant
h = 6.626 x 10^-34
The lower the frequency the ______ the wavelength.
higher
When a hydrogen atom is in an excited state, its electron is in one of the
higher-energy orbits
When a narrow beam of the emitted light was shined through a prism, it was separated into four specific colors of the visible spectrum. The four bands of light were part of what is known as the
hydrogen's emission-line spectrum
Niels Bohr proposed an idea that a
hydrogen-atom model that linked the atom's electron to photon emission
According to the Bohr model of the atom, electrons circle the nucleus
in specific, allowed orbits
in the bohr model of the atom, which orbit is an electron in its lowest energy state?
in the orbit closest to the nucleus
When a current is passed through a gas at low pressure, the potential energy of the gas atoms
increases
When an excited atom returns to its ground state,
it gives off the energy it gained in the form of electromagnetic radiation
Because air is mostly empty space, the value of 3.00 × 10^8 m/s is also
light's approximate speed through air
Because air is mostly empty space, the value of 3.00*10^8 meters per second is also
light's approximate speed through air
the higher the frequency, the ___ the wavelength
lower
depending on the type of electromagnetic radiation, it may be expressed in
meters, centimeters, or nanometers
a form of energy that exhibits wave behavior as it travels through space is
microwave radiation, ultraviolet radiation, and infrared radiation
A quantum of energy is the
minimum quantity of energy that can be lost or gained by an atom
The energy of the electron is higher when the electron is in orbits that are successively farther from the
nucleus
Quantum theory was developed to explain
observations such as the photoelectric effect and the line-emission spectrum of hydrogen
Bohr's model correctly the spectra of atoms with _________ electron(s)
one
The electron can circle the nucleus only in allowed paths, or
orbits
he energy of the electron is higher when it is in
orbits that are successively farther from the nucleus
a particle of electromagnetic radiation having zero mass and carrying a quantum of energy is called a
photon
When an electron moves from one main energy level to a main energy level of lower energy, a
photon is emitted
When light exhibits many wavelike properties, but it can also be thought of as a stream of particles. Each particle carries a quantum of energy. These particles are called
photons
Each particle carries a
quantum of energy
List the colors of light in the visible spectrum in order of increasing frequency.
red, orange, yellow, green, blue, indigo, violet
Because excited hydrogen atoms always produce the same line-emission spectrum, scientists concluded that hydrogen
releases energy of only certain values
The significant feature of wave motion is its
repetitive nature, which can be characterized by the measurable properties of wavelength and frequency
It was soon recognized, how ever, that Bohr's approach did not explain the
spectra of atoms with more than one electron nor the chemical behavior or atoms
Bohr's model of the hydrogen atom explained observed
spectral lines so well that many scientists concluded that the model could be applied to all atoms
In the equation, Quantum of Energy = hv,
the Quantum of Energy is in joules, v is the frequency, and h is a fundamental physical constant now known as Planck's constant; h = 6.626*10^-34
diffraction
the bending of a wave as it passes by the edge of an object or through a small opening
continuous spectrum
the emission of a continuous range of frequencies of electromagnetic radiation
The energy of a particular photon depends on
the frequency of the radiation
Explain the mathematical relationship among the frequency and wavelength of electromagnetic radiation
the mathematical relationship between frequency and wavelength is written as c = λν
Quantum of Energy
the minimum quantity of energy that can be lost or gained by an atom
Frequency (v) is defined as
the number of waves that pass a given point in a specific time, usually one second
What two experiments involving light and matter could not be explained by the wave theory of light
the photoelectric effect experiment and the hydrogen emission line spectrum experiment
Bohr's model did not explain
the spectra of atoms with more than one electron or the chemical behavior of atoms
in the equation c = λv, c represents
the speed of light
Because c=λv, we know that
v=c/λ
what color of light in the visible spectrum has the highest frequency?
violet
properties of light
wavelength and frequency
Light exhibits many
wavelike properties, but it can also be thought of as a stream of particles
Many of lights properties can be described in terms of
waves
Frequency is expressed in
waves/second
Process of emission
when an electron falls to a lower energy level
process of absorption
when energy must be added to an atom in order to move an electron from a lower energy level to a higher energy level
dual wave-particle nature of light
when light exhibits many wavelike properties, but it can also be thought of as a stream of particles. Each particle carries a quantum of energy
Orbits
when the electron can circle the nucleus only in allowed paths
interference
when waves overlap
5 examples of electromagnetic radiation
x rays, ultraviolet rays, infrared light, microwaves, radiowaves
Other kinds of electromagnetic radiation includes
x-rays, ultraviolet & infrared light, microwaves, and radio waves